Method of truing and dressing and abrasive wheel and apparatus therefor



Jan. 29, 1963 w. B. SEIDEL 3,075,512

METHOD OF TRUING AND DRESSING AN ABRASIVE WHEEL AND APPARATUS THEREFORFiled April 6, 1960 2 Sheets-Sheet 1 INVENTOR. WILLIAM B. SE/DELflTT'ORNEYS Jan. 29, 1963 w. B SE DEL 3,075,512

l METHOD OF TRUING AND DRESSING AN ABRASIVE WHEEL AND APPARATUS THEREFOR2 Sheets-Sheet 2 Filed April 6, 1960 United States Patent METHQD 0FTRUING AND DREfiLiHNG AN ABRA- l'VE WEEEL AND APPARATUS THEREFOR WilliamB. Seidei, Cincinnati, Qhio, assignor to The Cincinnati Milling Machine(10., Cincinnati, Ohio, a corporatiou or @hio Filed Apr. 6, 1960, Ser.No. 263% Claims. (Cl. 125-411.)

The present invention relates to a method of truing and dressing anabrasive wheel, and mechanism therefor.

In conventional diamond truing or dressing of an abrasive Wheel, adiamond is fixed in a holder which is moved across a surface of therotating wheel with the diamond in engagement therewith. The diamond isheld at a trailing angle relative to the surface of the wheel, and afacet is worn on the diamond. In most operations, as, for example,dressing the periphery of a cylindrical wheel, this facet is very nearlyflat and as the diamond wears, the area of the facet, or fiat,increases, increasing the area of contact between the diamond and thewheel.

The increased friction between the diamond and the wheel produces moreheat and promotes more rapid wear of the diamond. As the area of theflat in contact with the rotating wheel increases, fewer grains arefractured and flat surfaces are produced on many of the grains. Thus,the dressing, or sharpening, action of the diamond on the wheelprogressively deteriorates.

The truing, or shaping, action'of the diamond on the wheel is alsoimpaired in many conventional truing operations as the diamond wears.For example, in truing an arcuate contour on a Wheel with a tooltraversing the wheel in translation under control of a cam, reproductionof the cam conformation on the wheel becomes less precise as the span ofthe contact area of the diamond increases in the traversing direction.As the span of the contact area increases, more widely spaced regions ofthat area will engage the wheel at different portions of the contour asthe diamond moves transversely across the wheel and, although thediamond moves in conformity with the cam contour, the surface contouredon the wheel will not be a precise reproduction of the contour on thecam because different, transversely spaced, portions of the diamond haveformed, respectively, different portions of the wheel. Moreover, it isknown that a diamond offers a varying resistance to wear depending onthe orientation of the crystal structure thereof relative to thedirection of the abrading force, as described, for example, in US.Patent 2,889,822. In many contour truing operations different regions ofthe diamond are presented, at different orientations, to two or moreportions of the contour and the attrition rate of the diamond willdiiier in the two regions of the diamond, making precision truing evenmore diificult.

in order .to reduce the deleterious effects caused by the wear or" thediamond it has been customary periodically to index the diamond holderbetween operations on the wheel. In this manner the facet previouslyworn thereon is rotated an incremental amount relative to the rotatingwheel and a new facet is gradually formed on the diamond. The diamondagain progressively deteriorates in its dressing and truing action onthe wheel as the area of contact between the new facet and the wheelprogressively increases.

ferred form of the invention, a conical shaped diamond point is used.The diamond is oriented so that the cone defining the point establishessubstantially line contact with the wheel. The diamond :is rotated abouta central axis through the apex of the come as it is movedacross-the3,075,5i2 Patented Jan. 29, 1%53 face of the wheel so that no flat isworn on the diamond, and the shape of the diamond point, as well as thearea of contact between the diamond and the wheel, remains substantiallyunchanged.

In the diamond point, instead of excessive heat being generated in onelocalized region which is in continuous contact with the wheel, as inconventional diamond truing, the heat generated by the contact betweenthe tool and the wheel is distributed evenly over a substantially largersurface than the area in contact with the wheel. Since each region ofthe diamond point is in contact with the wheel only a small fraction ofeach revolution of the diamond, and is exposed to air or coolant for theremainder of each revolution, the heat generated in any region of thediamond point by contact with the wheel is continuously dissipatedduring the operation. With the heat generated by the action of thediamond on the wheel a distributed over the entire diamond point andeffectively dissipated continuously during the operation, wear of thediamond is reduced.

In the present invention where the diamond is rotated continuouslyduring operation on the wheel, uneven wear caused by the irregularresistance to wear of the diamond is minimized. When a soft region ofthe conical surface begins to wear more rapidly than a hard regionthereof, the hard region begins to bear a greater portion of the diamondaction on the wheel, and thus wear on the soft region is automaticallyreduced. This automatic compensation tends to maintain the conical shapeof the diamond. When the diamond is oriented so that the line contactbetween the diamond and the wheel is parallel to the direction-ofmovement of the wheel at the diamond and thus perpendicular to thedirection of traversing of the diamond across the wheel, the span of thesubstantially line contact between the conical diamond and the wheel inthe traversing direction is minute, permitting much more precise truingin operations where the diamond is moved in translation across acontoured Wheel.

Another advantage (and one more difiicult to understand) stems fromcontinuous rotation of the diamond while in engagement with the rotatingwheel. It has been found that with a rotating diamond a wheel isproduced which is substantially sharper, capable of many more grinds perdress, than would be expected from a wheel dressed with a diamond in theconventional manner. The precise action of the rotating diamond on thewheel is not fully understood but it is believed that the rotation ofthe diamond produces an additional force on the grains of the wheelwhich, when coupled with the fact that the diamond acts on a small (andunchanging) area of the 'wheel by virtue of the substantially linecontact therebetween, consistently produces a higher unit load on thegrains of the wheel to promote fracture thereof, without the formationof numerous fiat surfaced grains and the diminution of effectiveness ofdressing typical of conventional diamond dressing.

It is therefore one object of the present invention to provide animproved dressing method, and apparatus therefor, to produce a sharpgrinding wheel. It is another object of the present invention to providean improved dressing method, and apparatus therefor, to fracture thegrains of a grinding wheel in a manner to produce sharp pointed grains.It is still another object to provide an improved grinding wheel truingmethod, and apparatus, which maintains the shape of the truing tool. Itis another object of the present invention to provide an improved truingand dressing method by which heat is dissipated from the tool. It isstill another object to provide a truing and dressing method, andapparatus therefor, in which wear of the tool is minimized. Otherobjects and advantages of the present invention should be readilyapparent 'by reference to the following specification, considered inconjunction with the accompanying drawings forming a part thereof, andit is to be understood that any modifications may be made in the exactdetails there shown and described, within the scope of the appendedclaims, without departing from or exceeding the spirit of the invention.

In the drawings:

PEG. 1 shows a view, in perspective, of the diamond tool engaged withthe peripheral face of a cylindrical grinding wheel, with part of thediamond tool housing cut away for clarity;

FIG. 2 shows a greatly enlarged side elevation view of the diamond pointengaged with the peripheral face of the grinding wheel of FIG. 1;

FIG. 3 is a view taken on line 33- of P16. 2;

FIG. 4 is a view taken on line 44 of FIG. 2;

P16. 5 shows the diamond tool, in two different positions, as it movesacross a contoured wheel; and

FIG. 6 is a view taken on the line e-s of E18. 5 showing mechanism tomove the tool across the wheel, the tool being shown in its extremeright hand position.

There is shown in HG. 1, a dressing and truing tool, indicated generallyat it having a spindle ll, with a longitudinal central axis 12, thespindle having a diamond nib 13 mounted at one end. As shown in PEG. 2 adiamond 14 is mounted in the nib on the axis 12. As in truing with anonrotating diamond, axis 12 of the diamond tool is inclined relative tothe face of the abrasive wheel to be trued, or dressed, as, for example,the peripheral face 15 of the grinding wheel 16.

The spindle 11 may be operatively connected to an electric or hydraulicmotor for rotation thereby, but in the illustrative embodiment of theinvenuon disclosed herein, there is provided a simple, compact drive,capable of high speed, to rotate the spindle. With higher speeds ofrotation of the dimond during dressing, 2. better finish can be groundon a workpiece by the grinding wheel, because the effect on the grindingwheel of any slight irregularity of the diamond, or eccentricity ofrotation thereof, decreases as the speed of rotation of the diamondincreases. If, for example, one portion of the diamond is not completelyeffective in its action on the wheel, the diamond will be moved asmaller distance across the wheel while this less effective portion ofthe diamond is in contact with the wheel at higher angular speeds of thediamond. In operations where good finish on the workpiece is important,it is desirable to rotate the diamond at least at the angular speed ofthe grinding wheel and preferably faster. As shown in FIG. 1, thespindle 11 is mounted in a housing 17 by anti-friction bearings l8, l9,and 2t Turbine blades 21 connected to and radially extending from thespindle are received in a cylindrical chamber 22 in the housing. Chamber22 has tangentially oriented ports (not shown) circumferentially spacedapart and connecting, respectively, to an air inlet passage 23 and adischarge passage (not shown). Fluid, such as air, under pressure iscirculated through the housing and chamber 22 to rotate the turbineblades, and hence, the spindle and diamond.

The diamond 14 has a base portion 24 secured in the nib 13 byconventional means, and an extending shank Ed on axis 12. Since the axis12 is inclined relative to the peripheral face 15 which is to beoperated on, rotation of the spindle ill about the axis 12 with theextending shank 25 of the diamond in contact with the wheel willgenerate a surface of revolution on the diamond, the conformation ofsaid surface being determined by the profile of the wheel and the angleof inclination of the axis 12 relative to the wheel, and the diamond andthe wheel will be engaged in substantially line contact. The axis 12should be inclined at a trailing angle relative to the direction oftravel of the surface 15 (that is, as shown in MG. 1, inclined away fromthe direction of travel indicated by arrow A, of the surface 15 where itcontacts the diamond relative to a line 26 from the diamond through theaxis (not shown) of the wheel).- Preferably, the axis 12 is inclined sothat the substantially line contact between the diamond and the wheel,indicated at 27, is parallel to the direction of travel of the surface15 at the diamond, as shown best in H63. 2 and 3. The diamond may berotated in either direc- 'tion.

Preferably the extending shank 25 of the diamond is preformed to acylindrical, or substantially cylindrical, conformation, With a conical,or substantially conicai, point 29 having an apex so on the axis 12which constitutes the central axis of the shank and point. If the point29 is originally conical, and has one element of its cone parallel tothe tangent of the wheel where contacted by the diamond, the wheel willsoon generate the point 29 to establish substantially line contactbetween the diamond point and the wheel. Thereafter as the diamondwears, the conformation of the point 29 will remain substantially thesame, as indicated by dotted lines at 31, and, since the shank issubstantially cylindrical, the extent of the line contact between thediamond and the wheel will not be significantly increased so that theaction of the diamond on the wheel will not change. Although the sidesof the point 2) will be slightly curved, the point will remainsubstantially conical.

The tool It may be mounted in any conventional dressing or truingmechanism for movement, in either direction, across the surface to beoperated on in the same manner as a conventional dressing or truingdiamond. By way of example the tool 10 may be mounted in the tool holdershown and described in US. Patent 2,5 65,687 for movement in translationacross an arcuately contoured wheel 32 under the control of a cam, thespindle ll thereby being moved parallel to the surface of the wheel inclosely spaced relation thereto with the diamond in engagement with theworkpiece engaging periphery 35 of the wheel. As shown in FIG. 6, theslide unit 36 is mounted on the base unit 37 which has formed thereincylinder chamber 33. Chamber 3% receives a; piston 39 with a rod 49coupled to slide 35 for transverse actuation thereof. A truing toolslide housing 41 is slidably received in slide 36 and receives truingtool holder 42 in which the tool ill is mounted. The travers' ingdirection is perpendicular to the direction of movement of the wheelsurface at the diamond and, in truing an arcuately contoured wheel suchas wheel 32 in translation, the most precise truing is obtained when thesub stantially line contact between the diamond and the tool is parallelto the direction of movement of the wheel surface at the diamond, andhence perpendicular to the traversing direction. It should be noted thatwhen forming a contour having two slopes, such as 33 and 34 oriented atdifferent angles to a traversing diamond as it moves across the wheel intranslation, wear on one side of a nonrotating diamond point by contactwith one slope is likely to be significantly greater than wear on theother side of the diamond point by contact with the other slope becauseof the crystal orientation in the diamond, and the shaping, or truing,ability of the diamond rapidly deteriorates. Moreover, with theconventional nonrotating diamond, as a facet is worn on the diamond, oneside of the facet will shape slope 33 and the other side of the facetwill shape slope 34, impairing the precision of the truing operation asthe span of the facet increases in the traversing direction. However,with a rotating diamond oriented to establish substantially line contactwith the wheel perpendicular to the traversing direction, the shape ofthe diamond is maintained and the span of the diamond where it contactsthe Wheel is quite small in the traversing direction. This span does notincrease as the diamond wears and the ability of the diamond to produceprecise truing does not diminish as. the diamond wears.

In operation, the speed at which the wheel to be dressed or trued isrotated, and the rate at which the tool is traversed, or moved acrossthe wheel, maybe the same as used in conventional diamond truing anddressing. Any rotation of the diamond during the traverse of the wheelwill prolong the life of the diamond by continuously changing the regionof the diamond in contact with the wheel to facilitate continuousdissipation of generated heat. For better truing and dressing of thewheel, high speed rotation of the diam-0nd is desirable. In a typicaltruing and dressing operation, a wheel having, for example, an initialdiameter of 20 inches may be rotated at approximately 1250 revolutionsper minute to give an initial surface speed of about 6500 feet perminute, and the diamond may be traversed at a conventional rate of .0015inch per revolution of the wheel. The diamond which may, for example,have a diameter on the order of one-sixteenth of an inch at the base ofthe conical point, can be rotated at about 1600 revolutions per minute,and the axis of the diamond inclined 30 degrees from a line between thediamond and the axis of the wheel at a trailing angle.

What is claimed is:

1. The method of truing and dressing an abrasive wheel comprising thesteps of rotating the abrasive wheel, rotatably driving a substantiallyconical shaped diamond point about a central axis through the apex ofthe conical point independently of the rotating abrasive wheel, andmoving the rotatably driven diamond point across the Wheel with the sideof the conical point continuously in substantially line engagement witha moving surface of the rotating abrasive wheel, said diamond pointmoved at a trailing angle relative to the direction of movement of saidsurface with the line of engagement parallel to the direction ofmovement of said surface.

2. The method of truing and dressing a grinding wheel having a workpieceengaging surface comprising the steps of rotatably driving the grindingwheel, rotating a substantially conical shaped diamond point about acentral axis through the apex of the conical point of the diamondindependently of the grinding wheel and at a substantially constantangular speed, and moving the rotatably driven diamond point across thewheel in a traversing direction perpendicular to the direction ofmovement of the workpiece engaging surface at the diamond with the sideof the conical point continuously contacting the workpiece engagingsurface along a line parallel to the direction of movement of theworkpiece engaging surface at the diamond and with the diamond point ata trailing angle relative to said direction of movement of the workpieceengaging surface.

3. The method of truing and dressing a grinding wheel having a workpieceengaging surface comprising the steps of rotating the grinding wheel ata predetermined angular speed, rotatably driving a substantially conicalshaped diamond point about a central axis through the apex of theconical point of the diamond independently of the grinding wheel and at'a constant angular speed at least as great as the angular speed of thegrinding wheel, and moving the rotatably driven diamond point across thewheel for traversing perpendicular to the direction of movement of theworkpiece engaging surface at the diamond with the side of the conicalpoint continuously in substantially line contact with the workpieceengaging surface of the wheel, said diamond point moved at a trailingangle reiative to the direction of movement of said surface with theline of engagement parallel to the direction of movement of saidsurface.

4. In a machine tool having a rotatable abrasive wheel, a mechanism fortruing and dressing said wheel comprising a spindle having alongitudinal axis, a diamond having a substantially conical pointcarried at one end of the spindle with an apex on said axis, means tomount the spindle with the conical diamond point positioned for lineengagement with the surface of the wheel to be operated on, a driveconnected to the spindle to continuously rotate the spindle about itslongitudinal axis for rotation of the diamond, and means to move thespindle across the rotating Wheel with the rotating diamond engaged withthe surface of the wheel to be operated on at a trailing angle relativeto the direction of movement .of said wheel surface and with the line ofengagement between the diamond point and the wheel parallel to saiddirection .of movement of the wheel surface.

5. In a machine tool having a rotatable grinding wheel With .a workpieceengaging surface, a mechanism for truing and dressing said surfacecomprising a housing, means to traverse the housing across saidworkpiece engaging surface in spaced relation thereto, a spindlehaving alongitudinal axis and having a diamond at one end terminating in apreformed conical point with an apex on said longitudinal axis, means tomount the spindle in the housing for rotation about said longitudinalaxis, said spindle projecting from the housing for engagement of thediamond point with the workpiece engaging surface of the rotating wheelas the housing moves across said surface with the side of the conicalpoint contacting with said wheel surface along a line parallel to thedirection of motion of the wheel surface at the diamond andperpendicular to the traversing direction with the longitudinal axis ata trailing angle relative to the direction of motion of said surface atthe diamond, and a drive operat-ively connected to the spindle tocontinuously rotate said spindle for rotation of the diamond as thehousing is traversed across the wheel.

6. In a machine tool having a rotatable grinding wheel with a workpieceengaging surface, a mechanism for truing and dressing said surfacecomprising a spindle having a longitudinal axis, a diamond mounted atone end of the spindle with a substantially cylindrical extending shankterminating in a preformed conical point with an apex on saidlongitudinal axis, means to move the spindle across said workpieceengaging surface parallel thereto with the side of the diamond point incontact with said surface of the rotating wheel along a contact lineparallel to the direction of motion of said surface at the diamond pointand perpendicular to the direction of traversing movement with thediamond point at a. trailing angle relative to said moving surface, anda drive operatively connected to the spindle to rotate said spindle at asubstantially constant angular speed for rotation of said diamondcontinuously during engagement of the diamond with the wheel.

7. In a machine tool having a rotatable abrasive wheel, a mechanism fortruing and dressing said wheel comprising a housing, a spindle having alongitudinal axis mounted in said housing for rotation about said axis,a diamond carried at one end of the spindle on said axis, means defininga chamber in the housing, a plurality of radially extending blades onthe spindle and received in said chamber, means to circulate fluidthrough said chamber to rotate the blades and thereby rotate the spindleabout said axis, and means to move the housing across the wheel with theaxis of the spindle inclined at an angle relative to the surface to beoperated on and with the rotating diamond engaged with said surface ofthe rotating Wheel.

8. In a machine tool having a rotatable grinding wheel with a workpieceengaging surface, a mechanism for truing and dressing said surfacecomprising a housing, means to move the housing across said workpieceengaging surface in spaced relation therewith and parallel thereto, aspindle having a diamond mounted at one end with a substantiallycylindrical extending shank terminating in a preformed conical pointwith an apex on said longitudinal axis, means to rotatably mount thespindle in the housing for engagement of the diamond point with theworkpiece engaging surface of the wheel as the housing moves across saidsurface with the side of the conical point in substantially line contactwith said wheel surface and with the longitudinal axis at a trailingangle relative to the direction of motion surface at the diamond,

means defining a chamber in the housing, means defining a plurality ofturbine blades on the spindle in the housing, and means to circulate adriving medium through said chamber to rotate the spindle.

9. The method of truing and dressing a grinding wheel having a workpieceengaging surface comprising the steps or rotating the grinding Wheel ata predetermined speed, rotatably driving a substantially conical shapeddiamond point about a central axis through the apex of the conical pointof the diamond independently of the rotating grinding wheel and at anangular speed greater than the angular speed of the grinding wheel, andmoving the rotatably driven diamond point across the wheel fortraversing perpendicular to the direction of movement of said surface atthe diamond with the side of the conical point contacting the workpieceengaging surface of the wheel along a line parallel to the direction ofmovement of said surface at the diamond and with the diamond point at atrailing angle relative to said direction of movement of said surface.

10. The method of truing a grinding wheel having an arcuate workpieceengaging surface comprising the steps of rotatably driving the grindingWheel at a predeterg, mined speed, rotating a substantially conic-a1shaped diamond point about a central aXis through the apex of theconical point of the diamond independently of the grinding wheel and atan angular speed at least as great as the angular speed of the grindingwheel, and traversing the rotatably driven diamond point across thewheel in translation with the side of the conical point contacting theworkpiece engaging surf-ace of the Wheel along a line parallel to thedirection of movement of said surface at the diamond and perpendicularto the traversing direction with the diamond point at a trailing anglerelative to said direction of surface movement.

Rcfierences Cited in the tile of this patent UNITED STATES PATENTS1,833,667 Weinland Nov. 24, 1931 2,199,053 Meeson Apr. 30, 1940 FOREIGNPATENTS 136,806 Great Britain Feb. 18, 1921 417,451 Great Britain Sept.27, 1934 UNITED STATES PATENT OFFICE CERTIFICATE, OF CORRECTION PatentNo, 3,075,512 January 29, 1963 William B. Seidel It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Column 6, line 75, for "motion surface at the diamond" read motion ofsaid surface at the diamond Signed and sealed this 23rd day of April1963.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

1. THE METHOD OF TRUING AND DRESSING AN ABRASIVE WHEEL COMPRISING THESTEPS OF ROTATING THE ABRASIVE WHEEL, ROTATABLY DRIVING A SUBSTANTIALLYCONICAL SHAPED DIAMOND POINT ABOUT A CENTRAL AXIS THROUGH THE APEX OFTHE CONICAL POINT INDEPENDENTLY OF THE ROTATING ABRASIVE WHEEL, ANDMOVING THE ROTATABLY DRIVEN DIAMOND POINT ACROSS THE WHEEL WITH THE SIDEOF THE CONICAL POINT CONTINUOUSLY IN SUBSTANTIALLY LINE ENGAGEMENT WITHA MOVING SURFACE OF THE ROTATING ABRASIVE WHEEL, SAID DIAMOND POINTMOVED AT A TRAILING ANGLE RELATIVE TO THE DIRECTION OF MOVEMENT OF SAIDSURFACE WITH THE LINE OF ENGAGEMENT PARALLEL TO THE DIRECTION OFMOVEMENT OF SAID SURFACE.